Biphenylamide ligand complexes of Li and Al: hemilabile arene donors?

Biphenylamide ligands were employed to prepare a series of Li and Al derivatives in which the ligand binds through N. Such species include: (2-C(6)H(4)Ph)Bu(t)NLi (3), (2-C(6)H(4)Ph)Bu(t)NLi(THF)(2) (4), (2-C(6)H(4)Ph)Bu(t)NLi.OEt(2) (5), [(mu-(2-C(6)H(4)Ph)(2)N)Li](2) (6), (2-C(6)H(4)Ph)(2)NLi(THF)(2) (7), (2-C(6)H(4)Ph)(2)NLi.OEt(2) (8) amd (2-C(6)H(4)Ph)(2)NAlX(2) (X = Cl (9), Me (10), Et (11)). Structural and spectroscopic data show that these species exhibit weak arene to metal donation. This donor is hemilabile being readily displaced by other stronger donors to give such species as (2-C(6)H(4)Ph)(2)NAlMe(2)(THF) (12) and (2-C(6)H(4)Ph)(2)NAlMe(2)(CH(2)PPh(3)) (13). Reactions of 10 with B(C(6)F(5))(3) results in methyl for C(6)F(5) exchange and isolation of (2-C(6)H(4)Ph)(2)NAl(C(6)F(5))(2) (14). The presence the electron withdrawing groups in 14 further strengthens the hemilabile interaction.